Yam Chips Research Articles

Effects of cassava starch gel on physical and textural properties of coated yam chips

The objective of this study was to transform two varieties of yam, “Anader” (Dioscorea cayenensis rotundata) and "Bètè-Bètè" (Dioscorea alata), into industrially viable products. The objective was to produce yam chips coated with cassava starch gel (at concentrations of 2%, 3%, and 4%) with a minimal oil content. Yam slices were blanched at 70°C for one minute, following which they were coated with gels prior to undergoing a frying process. "Anader" (Dioscorea cayenensis rotundata) variety was fried at 160°C for a period of ten minutes, while "Bètè-Bètè" (Dioscorea alata) variety was fried at 150 °C for the same length of time. Results showed that the coating effectively reduced oil content of the chips while maintaining an adequate water content. Oil content of the uncoated chips (control) was found to be 35.71±0.07% for "Bètè-Bètè" (Dioscorea alata) and 25.10±0.10% for "Anader" (Dioscorea cayenensis rotundata), respectively. However, oil content of the chips coated at 4% was 31.83±0.13% and 24.54±0.04% for the same varieties, respectively. Furthermore, the greatest reduction rates were achieved with 4% cassava starch gel, resulting in a 10.86±0.20% reduction for "Bètè-Bètè" (Dioscorea alata) variety. Texture parameters (hardness, fracturability and deformation) also exhibited notable discrepancies in accordance with the varying gel concentrations employed. Cassava starch gel reduced oil absorption and improved the texture of the chips, enhancing their quality. Finally, this easy-to-use, based on local resources, coating makes yam chips healthier and more appealing to health-conscious consumers.

Insect pests of dried yam (Dioscorea sp.) chips and the perception of processors and marketers on their control

This survey was aimed at understanding the perception of Dried yam chips (DYC) Processors and Marketers on insect pests' infestation of DYC and their damage through the use of structured questionnaires. Data on socio-economic characteristics and technical information were analyzed using descriptive statistics such as frequency distribution, percentages, and means. Data on the perception of insect pests and measures of pest control were placed on a 3-point Likert Rating Scale (LRS). Analysis of variance (ANOVA) was done on the population density of the identified insects and significant mean values were compared using Fisher's Least Significant Difference. Seven insect pests; Prostephanus truncatus, Rhyzopertha dominica, Tribolium castaneum, Stegobium paniceum, Heterobostrychus aequalis, Sitophilus zeamais, Areacerus fasciculatus, and one natural enemy; Peregrinator biannulipes were associated with DYC. However, P. truncatus, R. dominica, and A. fasciculatus were the most prevalent insect pests, causing significant damage to DYC. Approximately, 49% of processors reportedly control insect infestation in DYC using conventional insecticides, 23% by re-drying, 14% by botanicals, and the others by removing affected DYC. These findings provide useful information for extension workers involved in community education, and intervention programs by government or non-governmental organizations including public health experts and researchers.

Microbiological Quality of Dehydrated Yam (Dioscorea rotundata) Chips As Affected By Different Pre-Treatments During Storage

Microbiological Quality of Dehydrated Yam (Dioscorea rotundata) Chips As Affected By Different Pre-Treatments During Storage

Combined effects of the assassin bug alloeocranum biannulipes mont. And sign. (hemiptera: reduviidae) and botanical powders in the control of the stored yam chips beetle, dinoderus porcellus lesne (coleoptera : bostrichidae)

Background Dinoderus porcellus Lesne (Coleoptera: Bostrichidae) is the main pest of stored dried yam chips that causes significant losses in a few months. The assassin bug, Alloeocranum biannulipes (Montrouzier & Signoret) (Hemiptera: Reduviidae) and the Khaya senegalensis (Desv.) A. Juss. (Meliaceae), Blighia sapida K. Koenig (Sapindaceae) and Bridelia ferruginea Benth. (Euphorbiaceae) leaf powders have proven to be efficient in the control of this pest. Methods This study aims to evaluate the compatibility of the leaf powders of these medicinal plants and the predator A. biannulipes in the integrated management of D. porcellus under laboratory and farm conditions. Various leaf powders were tested at a concentration of 6% (w/w) with or without the predator. Yam chips mixed with leaf powder from each species served as negative and those mixed with a synthetic insecticide as positive controls. Results The results revealed that no combination of leaf powders and predators could induce complete mortality of D. porcellus like the synthetic insecticide. No significant difference in terms of the survival of A. biannulipes exposed to botanical powders was observed compared to the positive control. Under farm conditions, B. ferruginea leaf powder showed a sub-lethal effect on the predator A. biannulipes and no impact on the abundance of D. porcellus. However, the survival of D. porcellus was significantly reduced by the combination of K. senegalensis leaf powder and A. biannulipes, which did not allow the reproduction of the predator. Conclusions We recommend the combination of K. senegalensis leaf powder and A. biannulipes for the short-term conservation of yam chips as part of an augmentative biological control program. For long-term conservation, we suggest the use of a combination of B. sapida leaf powder with the predator A. biannulipes because it presented a reduced population of D. porcellus after 8 weeks of storage and offspring of A. biannulipes.

Agronomic performance and consumer acceptability of improved water yam (Dioscorea alata L.) varieties in the Republic of Benin

White yam (Dioscorea rotundata L.) is widely cultivated, and is a staple food in the Republic of Benin. However, its production is highly sensitive to soil infertility, leading to low yields over the years. In order to address the challenges of land reduction and climate change, it is crucial to introduce more adapted yam varieties to traditional Beninese agriculture. Water yam (Dioscorea alata L.) varieties are viable options, as they need less soil fertility and yield more than D. rotundata, but have a poor culinary performance. The aim of this study is to assess the agronomic and culinary performance of 15 improved water yam genotypes developed by the International Institute of Tropical Agriculture (IITA) compared to local cultivars. In 2022 and 2023, multilocal trials (4 sites) were performed in the yam-growing areas, and nine villages were selected for culinary evaluation. Linear mixed-effects models and generalized mixed-effects models showed significant differences (p < 0.05) in location, year of experimentation, and certain evaluated agronomic parameters. The improved varieties had a strong likelihood of producing small tubers that could be used as seeds. The agronomic and culinary performance of local water yam accessions has been superior to that of improved varieties. Due to its numerous medium tubers, TDa_1508044 could be introduced for production of yam chips. TDa_1510080, which showed a stable high yield throughout the trial sites, and TDa_1510119, which gave a great number of marketable large-size tubers, showed the best agronomic performance with a yield of more than 25 t/ha. TDa_1510043, TDa_0000194, and TDa_1515030 improved varieties that performed well in both culinary and agronomic ways could be widely adopted by farmers in the yam-growing areas of Benin.

Modelling convectional oven drying characteristics and energy consumption of dehydrated yam (Dioscorea rotundata) chips

The influence of pre-treatments and different dehydrating temperatures on the drying dynamics, energy consumption, and quality attribute of yam chips was studied. Dehydration was executed employing a convectional oven dryer under four temperatures (50, 60, 70, and 80 °C) and 2.0 m/s air velocity. Yam chips were subjected to pre-treatment conditions of blanching (for 1, 2, 3, 4, and 5 min), citric acid (1 and 5 %), and ascorbic acid (1 and 5 %) solutions whereas, untreated yam chips samples served as the control. Dehydrated yam chips were further assessed for textural and colour properties. The drying rate was found to be faster at a higher temperature of 80 °C compared to lower temperatures of 50, 60, and 70 °C. The asymptotic model was established to be the suitable descriptive model for predicting moisture profile in the pre-treated yam chips based on highest R2 values (0.995–0.999), lowest χ2 values (4.422–18.498), and the root mean square error (RMSE) values (2.103–4.30). Pre-treatment and drying temperature had a significant (p <0.05) impact on the hardness and colour of dehydrated yam chips. Blanching at 4 min yielded yam chips with most preferred texture (hardness: 81.3 N) and lightness (L*) in colour values (71.07 %) after drying compared to other pre-treated samples. The effective moisture diffusivity values of the pre-treated samples were in the range of 5.17294 × 10−9m2/s to 1.10143 × 10−8m2/s for 5 % citric acid samples at 50 °C and all pre-treated samples at 80 °C respectively. The general findings of the study indicated a least energy usage of 43.68 kWh as a cost-effective method of drying. Also, 4 min blanching, 5 % citric acid, and 1 % ascorbic acid at 80 °C were found to be the optimum conditions for pre-treating yam chips based on lower energy level consumption rates and improved sensory properties thus attributing to the quality of the dried yam chips.

Resistance of Dried Chips of Three Yam Cultivars to Damage by Prostephanus truncatus (Horn) (Coleoptera: Bostrichidae)

Yam (Dioscorea spp) is one of the most common tuber crops consumed by man due to its nutritional benefits. Yam tubers are often processed into products like Dry Yam Chips (DYC) to minimize postharvest losses. The crop could be processed into other products to reduce perishability and scarcity at certain periods. The insect is mainly controlled with conventional insecticides. However, use of conventional insecticide in preserving DYC is contentious due to concerns about undesirable effects on consumers. This has necessitated the search for safer and more effective control strategies such as resistance traits that is innate. The study was therefore conducted to evaluate the resistance of three yam species (Dioscorea cayenensis, D. rotundata, and D. alata) used in making DYC to infestation and damage by Larger Grain Borer (LGB). Two hundred (200) g of parboiled DYC were weighed into 250 ml Kilner jars and separately infested with twenty adult LGB of 0-5 days old. The treatments were replicated four times and arranged on the experimental table using Completely Randomized Design (CRD). At 90 days post-infestation, the insects were sieved out to separate insects from DYC. Data were collected on weight loss of DYC, damage to DYC, adult mortality of LGB, dust of DYC, and number of emerged LGB. The percentage damage of LGB to DYC of D. alata and D. rotundata was 100.00% and 96.43%, respectively, which were not significantly (p&gt; 0.05) different from each other. The percentage weight loss (70.61) of DYC of D. alata was significantly (p&lt; 0.05) higher than the weight loss in D. cayenensis (28.63) and D. rotundata (46.27). The percent weight loss in the DYC of D. cayenensis was significantly (p&lt; 0.05) lower than the weight loss in DYC of D. alata (70.61) and D. rotundata (46.27). The number of adult LGB (539.80) in the DYC of D. alata was significantly (p &lt; 0.05) higher than the number of the insect in D. cayenensis (117.8) and D. rotundata (216.80). The number of adult mortality of LGB in the DYC of D. alata (38.50) and D. cayenensis (21.12) is comparable, but significantly lower than number of adult mortality of the insect in D. rotundata (41.50) DYC. The number of the insect larvae in DYC of D. cayenensis (4.25) was significantly (p&lt; 0.05) lower than the number of the larvae of LGB in DYC of D. alata (30.00) and D. rotundata (21.00). DYC of D. cayenensis and D. rotundata were moderately resistant to damage by LGB and could be use in preparation of DYC to mitigate damage of LGB to DYC in storage before use.

Evaluation of yam (Dioscorea rotundata) chips pre-treatment conditions (salting, sulphiting, and blanching) combined with dehydrofrozen storage for fries production

Evaluation of yam (Dioscorea rotundata) chips pre-treatment conditions (salting, sulphiting, and blanching) combined with dehydrofrozen storage for fries production

Health Implication of Mycotoxigenic Fungi and Mycotoxins Analysed from Sun Dried Yam and Potato Chips Sold in Minna Niger State, Nigeria

Mycotoxin is toxic secondary metabolite synthesized by filamentous fungi during their stationary phase of growth in agricultural crops, food and feed products. Niger State experienced high temperature and humidity for about three-quarters of the year, and these are some of the conditions that encourage filamentous fungi to produce mycotoxin in food products. Enzyme Linked Immunosorbent Assay (ELISA) was used to dectect mycotoxins. Mycological profile and mycotoxins of sun dried yam and potato chips was determined. Total of fifty (50) samples were collected randomly from five markets in Minna and its environs. 179 isolates were recorded. Aspergillus species 86(53.1 %) Mucor species 27(15.1 %), yeast species 25(13.9 %) Penicillium species 14(7.8 %), Fusarium species 14(7.8 %) Rhizopus species 3(1.7 %) and Microsporum species 1(0.6 %) were the common fungi. The highest mean fungal counts (12.8 x 103 cfu/g) were observed in sweet potato chips bought in Gwada market while the lowest (3.5 x 103 cfu/g), was observed in Yam chips from Paiko market. The mean moisture content of 7.41±2.28 % was recorded in potato chips and yam chips had the lowest moisture content of 4.72± 1.66 %. Total aflatoxins, fumonisin and zearalenone contents were detected in 48 (96 %) of the samples. In yam and potato chips, total aflatoxin contamination was 68 and 84 % with mean concentrations of 12.6±7.36 μg/kg and 10.3±13.81 μg/kg respectively. The total aflatoxin concentration range of yam and potato chips were 0-61.84 μg/kg and 0-54.49 μg/kg with 28 and 48 % of the samples below 4μg/kg E.U limit respectively. Fumonisin contamination was 80 and 60% with mean concentrations of 928.123±559.50 μg/kg and 722.64 ± 137.85 μg/kg with a range 0.0-4018.24 μg/kg and 0 – 2055.98 μg/kg and had 52 and 72 % below 1000 μg/kg acceptable limit for yam and potato chips respectively. Zearalenone contamination in yam and potato account for 56 and 68% having mean concentration of 16.33± 9.71 μg/kg and 24.12± 21.03 μg/kg with a range 0 – 45.53 μg/kg and 0 – 83.74 μg/kg respectively. All the samples contaminated with Zearalenone were below the E.U regulatory limit of 100 μg/kg for food stuff intended for direct consumption. Dietary exposure and risk characterisation (EDI and %TDI) were further estimated for total aflatoxins, fumonisin and zearalenone. It was concluded that the level of contamination of these chips with mycotoxins poses a serious threat to public health and there is the need for proactive approach to drastically reduce fungal contamination.

EVALUATION OF LEVEL OF RANCIDITY OF EDIBLE OIL IN SOME FRIED SNACKS FOOD

This work evaluated the level of rancidity of edible oil in six (6) fried snacks food, namely, beans cake (Akara), groundnut cake (Kuli-kuli), bread buns, fried fish, fried yam chips and fried potatoes chips, purchased from hawkers in Wukari, Taraba State, Nigeria.. The rancidity indicators and their ranges in the samples obtained, include, Acid Value (4.10 – 6.90 mgKOH/g), Free Fatty Acid (2.05 – 3.45 mgKOH/g), Peroxide Value (12 – 46.60 mEq/kg), Moisture Content (4.00 – 44.30 %), Conductivity (0.14 – 1.58 µS/cm) and Viscosity (26.20 – 56.50 mm2/S). The results obtained suggested that the fried snacks foods contain hazardous secondary oxidative products, an implication that the oil in the food sample has become rancid and as such, unsafe for human consumption. The reason given for this is that the oil has been used for frying for too many times instead of the recommended two times. The values obtained in this study far exceeded the stipulated standard acceptable ranges given by WHO, FAO and INSO. It is therefore recommended that the public should be advised and educated that oil that has been used for frying twice should be discarded and not used again. Also, Policy makers and relevant authorities should develop a device for in-situ determination for checking of the quality of oil used for fried snacks food in restaurants without going to the laboratory.

Effect of organic acid pre-treatment on polyphenol oxidase induced browning and sensory quality of frozen yam chips

Yam Dioscorea spp suffers about 30% postharvest losses annually. Processing into convenience products such as yam chips prolong shelf life although the action of enzymes including polyphenol oxidase (PPO) and peroxidase (POD) may affect the quality if not precluded. Pre-treatment of cut yam with pH modifiers and antioxidants before storage could reduce enzymatic browning. In this study we investigated the effectiveness of ascorbic acid, citric acid and lime juice treatment and 5 weeks (w) of frozen storage in reducing browning in yam chips without affecting sensory quality. PPO and POD activity of freshly prepared yam chips pre-treated with citric acid, ascorbic acid or lime juice and stored frozen at -18 °C for 5 weeks was determined. The yam chips were fried and the moisture, oil content and colour determined. Consumer acceptability sensory evaluation was conducted for the week 0 and 5 of stored samples. POD activity was significantly reduced (50%) by treatment with citric acid after five-weeks of frozen storage while treatment with ascorbic acid and lime juice had no effect on the enzyme activity. There was no significant difference in lightness between the different treatments although treated samples differed significantly from the untreated. Moisture content of all samples were lower after storage while oil content of the various treatments was significantly different. Notwithstanding these differences, consumer acceptability was not different between the various treatment and storage periods. Pre-treated frozen yam chips have a good consumer acceptance and potential for commercial application. Developing this product will add value to yams and reduce huge postharvest losses.

Potential of Metarhizium anisopliae and Beauveria bassiana to control Dinoderus porcellus (Coleoptera: Bostrychidae) infesting yam chips

• B. bassiana (Bb115) and M. anisopliae (Met31) isolates are promising biological control agent of D. porcellus . • Bb115 and Met31 isolates at all concentrations caused more than 50% mortality at 7 days post-inoculation. • LT 50 values for Bb115 and Met31 isolates were 2.63 and 3.35 days, respectively. • Bb115 isolate showed the lower LD 90 values and the highest rates of cadaver sporulation. • Bb115 isolate at 10 9 conidia/mL reduced D. porcellus populations and weight loss of stored yam chips. The beetle Dinoderus porcellus Lesne is a serious storage insect pest that causes important losses by destroying stocks of yam chips. In the aim to found an alternative control method to the use of synthetic insecticides for its management, the virulence of the entomopathogenic fungi Beauveria bassiana (Balsamo) Vuillemin (isolate Bb115) and Metarhizium anisopliae (Metschnikoff) Sorokin (isolate Met 31) against adults of D. porcellus was evaluated under laboratory conditions (25 ± 2 °C and 70 ± 5% RH). Then, the effectiveness of the most virulent entomopathogenic fungus as biological agent against D. porcellus was assessed under farmer storage conditions. For each entomopathogenic fungus isolate, four conidial concentration (0, 10 5 , 10 7 , and 10 9 conidia/mL) at the dose of 1 µL were inoculated topically on D. porcellus adults (3–5 days old). Observations focused on insect mortality, cadaver sporulation and weight loss of yam chips. Lethal dose and lethal time values were estimated using probit analysis. Both fungal isolates at all conidial dose caused more than 50% mortality on day 7, with the highest mortality (94.44%) achieved using B. bassiana at the 10 9 conidia/mL. LT 50 values for B. bassiana and M. anisopliae isolates were 2.63 and 3.35 days, respectively, while their LT 90 values were 6.15 and 9.87 days, respectively. Yielding the lower LD 90 values and the highest rates of cadaver sporulation, B. bassiana isolate appeared as the most virulent against D. porcellus . After 3 months of storage, comparatively to the control, the B. bassiana isolate at the highest conidial dose (10 9 conidia/mL) significantly reduced D. porcellus populations, and weight loss of yam chips. This study revealed the potential of B. bassiana and M. anisoplae isolates as biological control agent against D. porcellus for yam chips protection.

Rancang Bangun Sistem Pengering Bengkuang Sebagai Olahan Keripik Berbasis Mikrokontroler

This research was conducted with the aim of drying jicama as a processed yam chips. The condition of the yam dried in an open space with low temperatures resulted in the growth of fungus on the surface of the jicama. The growth of mushrooms on jicama makes it unable to be processed and consumed. Therefore we need a system that can dry yam with a drying machine. This system can monitor the water content of jicama using a soilmoisture sensor and measure the temperature with the DS18B20 sensor in the drying room. Jicama is said to be dry when the water content is &lt;10%, when the moisture content value (&gt; 25%) then the jicama is wet, if the water content of the jicama (10.1% ≤ KA ≤ 25%) then the jicama is in a humid condition, so that the fan, heater and DC motor turns on. This tool is designed using the Arduino Uno, DS18B20 sensor, Soilmoiture sensor, heater, DC fan, DC motor, buzzer, relay, LCD. When the temperature is&gt; 60 ° C, the DC Heater and Fan will turn off to reduce the temperature. The results of the yam condition will be displayed on the LCD. This is expected to be able to dry jicama quickly and produce dry jicama with good quality.

Aflatoxin Total and Microbial Contamination of Grains, Oil Seeds, Yam Chips and Fish Sold in Maiduguri Market

Aflatoxins are secondary metabolites of fungus Aspergillus flavus and closely related species that infects severalagricultural commodities. The consumption of contaminated commodities adversely affects the health of humansand animals and also a cause of significant economic losses to producers. This study surveyed the aflatoxincontamination level of cowpea, maize, melon, groundnut, yam chips and fish sold in Maiduguri metropolis.Samples from each product (250 g) were bulked and thoroughly mixed using coning and quartering method to geta representative sample for analysis. Laboratory observations were carried out regarding microbial analysis,proximate composition and aflatoxin content. Samples for aflatoxin detection were classified into three; unsortedsamples, sorted samples and sorted/washed dried samples. Fish had the highest bacterial load 2.48 x 106 cfu/ml andAspergillus species were found to be the predominant fungi identified. Maize and groundnut with moisture contentof 5.63 and 5.62 had the highest total aflatoxin contamination (320.51 μg/kg and 236.3 μg/kg respectively) both inthe unsorted group. Total aflatoxin reduction of (58.82 - 99.99%) was observed in all the sorted samples andsorted/washed dried samples. It can be concluded that commonly sold food in Maiduguri had fungal and Aflatoxincontamination. Food should undergo several rounds of sorting to remove discoloured grains and grains that showsevidence(s) of deterioration to reduce the ingestion of food contaminated with aflatoxin.

Pesticide Potential of Gmelina arborea Stem Bark and Leaf Powder against

Insect pest are a major problem to food security, most especially in developing countries like Nigeria. There is an urgent need towards mitigating the effects of these group of insects, and botanical extracts had played an increasing role as an alternative insecticide. The aim of the present study is to investigate the anti-feeding effect of different dosage of Gmelina arborea stem bark and leaf powder against Dinoderus porcellus infesting yam chips. The study was conducted at the Entomology Laboratory of Federal College of Forestry, Jos. Soxhlet extraction using methanol was used to extract plant part samples. Presence of phytochemicals contained in the plant were examined following standard protocols. The antifeedant effects of different dosage of Gmelina arborea leaf and stem bark powder on Dinoderus porcellus was determined by monitoring yam chips weight loss. Data collected was subjected to analysis of variance (ANOVA) at 1 % level of significance and the means separated using Duncan test. The results revealed presence of tannin, flavoid, saponins, alkaloids, reducing sugar and phenol with absence of steroid. The results also revealed that the various dosages have remarkable antifeedant effect on the development of D. porcellus. The weight loss of treated yam chips was significantly different from those of untreated yam chips. Therefore, the results obtained in this work accounts for the use of G. arborea plant parts powders as bio-preservative for yam chips against D. porcellus.

Effect of population density on oviposition, development, and survival of Alloeocranum biannulipes (Hemiptera: Reduviidae) preying on Dinoderus porcellus (Coleoptera: Bostrichidae)

BackgroundAlloeocranum biannulipes Montr. and Sign.(Hemiptera: Reduviidae) is a predator present in stored yam chips and a promising biological control agent against Dinoderus porcellus Lesne (Coleoptera: Bostrichidae). Numerical responses of A. biannulipes to different densities (1, 2, 4, 6, and 8) of D. porcellus larvae were evaluated under ambient laboratory conditions (T°: 25 ± 2 °C; RH: 75–80%; photoperiod 12:12 h (L/D)). The number of consumed prey, duration of pre-oviposition and oviposition, number of eggs laid, pre-imaginal development times and mortality rate of the predator were recorded.ResultsThe results revealed that A. biannulipes females preying on the highest larval density of D. porcellus (8) presented the highest predation rate (4.34 ± 0.18 larvae/predator/day), shortest pre-oviposition period (11.01 ± 0.57 days) and the highest oviposition period (15.83 ± 1.02 days). The daily number of eggs laid by A. biannulipes female (y) as a function of the number of D. porcellus larvae consumed (x) was modelled by the equation y = 0.158x2 – 0.4073x + 3.8151 (R2 = 0.571). The efficiency of prey conversion into eggs of A. biannulipes females decreased with increased prey density. The prey density did not affect the hatching rate of A. biannulipes eggs and the pre-imaginal development times. However, A. biannulipes nymphs fed with more (2 to 8) D. porcellus showed a significantly higher survival rate than those fed with a single larva.ConclusionsThe positive numerical response of A. biannulipes suggests that this predator could play a key role in biological control program against D. porcellus.

A Comparative Technique for Performance Evaluation of Hammer Mill and Disk Mill in Yam Flour Processing

Grinding (Particle size reduction) of biomass is an age-long operation that is performed during the preparation process of certain food products. Among the grinding mill machines mostly used for this operation are hammer mill and disk mill. Being that the nature of biomass affects the performance and choice of grinding-mill machine to be adopted, it is imperative to compare and select appropriate grinding mill machine that is efficient and effective. In this paper, a comparative technique to evaluate and select appropriate grinding mill machine for particle size reduction of dried white yam (Dioscorea rotundata) is proposed. Hammer mill and disk mill machines were selected for consideration. Two white yam species (Benue and Delta Yam) were prepared into dried chips and ground using the selected mills. Among the attribute (performance parameters) considered are crushing time, particle size distribution and energy consumed. A measure of performance (Index I) based on the comparative technique was formulated and used in evaluating the performance of the two mills. In the hammer mill, index I recorded 2721.2 and 3719.82 par/kWh for Benue Yam chips at screen size 4 and 6 mm, respectively, while 2647.89 and 3472.01 par/kWh was recorded for Delta yam chips at screen size 4 and 6 mm, respectively. Index I values for the Disk mill were 2536.25 and 2433.42 par/kWh at 1.2 mm clearance distance for Benue Yam chips and Delta Yam chips, respectively. The results indicated that hammer mill performed better overall than the disk mill. The comparative technique was found suitable in the evaluation of the performance of the mills. It is recommended that hammer mill be adopted.

Cyanogenic compounds removal and characteristics of non- and pregelatinized traditional detoxified wild yam (Dioscorea hispida) tuber flour

The presence of cyanide compounds restricts the utilization of wild yam (Dioscorea hispida) tubers for food or food ingredients. Traditional detoxification, usually used in wild yam chips processing, has not been evaluated for its effectiveness in reducing cyanogenic compounds. Processing into flour will increase wild yam tubers utilization and pregelatinization usually improve flour functional properties. This study aimed to evaluate the effect of 4 traditional detoxification methods and pregelatinization on cyanogenic compounds removal and wild yam tuber flour characteristics. The different methods were in rubbing ash, soaking time, and pregelatinization methods by boiling or steaming. The duration of a particular step was also different. The results showed that traditional detoxification methods reduced total cyanides 97%, cyanogenic glycosides 98-100%, acetone cyanohydrin 89-97%, and HCN 94-95%; also affected degree of cyanogenic compounds removal. Pregelatinization also reinforced the degree of cyanogen removal. Tuber flour physicochemical properties were affected by detoxification methods and pregelatinization. Modification of starch might occur due to the presence of SiO2 and calcium in rubbing ash and affected functional properties of wild yam tuber flour. Starch granule morphology appeared not to be affected by detoxification methods. Traditional detoxification methods could be used to make a safe wild yam tuber flour.

Effects of four agro-botanical extracts and three types of storage sacks on the control of insect pests and mould of stored dried yam chips

Effects of four agro-botanical extracts and three types of storage sacks on the control of insect pests and mould of stored dried yam chips

Compared efficiency of a commercial Neem oil (TopBio) and synthetic insecticide (Antouka Super) in the management of Dinoderus porcellus Lesne (Coleoptera: Bostrichidae) infesting yam chips

Dinoderus porcellus Lesne is the main pest of stored yam chips in West Africa. Despite their negative impact on the environment and human health, synthetic chemical pesticides are the main control method used by farmers for yam chips protection. This study aims to evaluate the biological effects of different doses (2.5 and 5%) of a commercial Neem oil (TopBio) and the chemical insecticide, Antouka Super® (Permethrin 3 g / kg + pyrimiphos 16 g / kg) against D. porcellus fed on yam chips. We evaluated the contact toxicity by topical application, the repellent activity, and ingestion toxicity of both products. Results revealed that D. porcellus adults were more sensitive to contact with Neem oil (LC50 = 2.17 μl/adult) than with the chemical insecticide (LC50 = 644.93 μl/adult) at 72 h post-treatment. The Neem oil (TopBio) also exhibited a strong repulsion (Class V) against D. porcellus at all tested concentrations. Antouka Super® at 5% was more effective against D. porcellus by ingestion with a corrected mortality percentage of 81.05 ± 11.00% three days post-treatment versus 15.73 ± 11.36% with Neem oil. The lowest weight loss of treated yam chips was obtained with Antouka (0.06 ± 0.02%) comparatively to the Neem oil at 5% (2.12 ± 0.42%). Our study showed that Neem oil (TopBio) is a contact biocide with a highly repulsive potential for integrated management of D. porcellus adults in stored yam chips. Key words: Dinoderus porcellus, yam chips, contact toxicity, repellency, ingestion, bioinsecticide.